Retrievable through tubing tool and method

ABSTRACT

Retrievable window cutting apparatus and method include a whipstock assembly 160 and anchor assembly 10. Whipstock assembly 160 and anchor assembly 10 contract radially inwardly to pass through tubing string T and then expand radially outwardly to operate in casing C. Upper and lower independently moveable slips 24 and 26 engage casing C. Whipstock assembly 160 includes hinge assembly 170 that can be set for operation with a milling assembly 270. Cooperation between shear members in setting tool WSS, working string adaptor 180, hinge assembly 170, and anchor assembly 10 provide for keeping whipstock assembly 160 and anchor assembly 10 in a contracted position for passing downwardly through tubing T, expansion in casing C, and subsequent retrieval through tubing T.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/223,704 filed Apr. 6, 1994 for a THRU TUBING TOOL ANDMETHOD, now U.S. Pat. No. 5,566,762.

FIELD OF THE INVENTION

The present invention relates generally to a through tubing assemblyoperable for cutting a casing window and, more particularly, toapparatus and methods relating to a retrievable through tubing whipstockassembly.

DESCRIPTION OF THE BACKGROUND

A whipstock may generally refer to a device inserted in a wellbore thatis used for deflecting a drill bit or mill in a direction that isangularly offset with respect to the orientation of the originalwellbore so as to establish a new or additional drilling course. In mostinstances, a whipstock procedure involves setting an anchor andproviding an angled whipstock surface supported by the anchor at thedesired depth in the wellbore to conduct side track or lateraldirectional drilling operations through the casing string.

It is frequently desired to cut or mill a window in a casing string thatalso includes therein a smaller diameter tubular string, such as forconducting wellbore fluids, that terminates at a position above thedesired position of the window. It has typically been necessary to firstremove the tubular string from the wellbore prior to performing thewhipstock operation. Removal of the tubular string requires considerablerig time and expense, but is required to permit the entry of a full-borewhipstock assembly into the casing for positioning at the desired depthfor then milling or cutting a window in the casing.

The face of the whipstock is oriented to position the casing window at adesired radial azimuth relative to the borehole axis in accordance withthe new course of drilling. With the casing window properly positioned,the side track or lateral drilling operation may proceed in the desiredazimuthal direction relative to the borehole. The face of the whipstockmay be oriented using a multiple trip operation into and out of thewellbore.

The setting of anchors and whipstocks for purposes of milling windows inthe casing string has been performed for many years. However, apparatusand methods have not heretofore existed that permit milling a window inthe casing string by passage of a retrievable whipstock assembly througha smaller diameter tubular member, such as a production tubing stringpositioned within the casing. As well, more reliable apparatus andmethods are desired for setting an anchor and a whipstock assemblywithin a casing positioned downhole by passing through a smallerdiameter tubular member, such as a production string.

Consequently, there remains a need for apparatus and methods that offerthe drilling industry the flexibility to reduce drilling time and costsby allowing installation and removal of a whipstock assembly at adesired position in the casing, and for reliably setting a whipstockassembly passed through a smaller diameter tubular member. Those skilledin the art have long sought and will appreciate the present Inventionwhich provides solutions to these and other problems.

SUMMARY OF THE INVENTION

The downhole tool and method of the present invention may be used to cuta window, such as a casing window, in a tubular disposed in a wellbore.For this purpose, the method provides for retrievably positioning adownhole tool within a first tubular supported within a wellbore, thefirst tubular having therein a second tubular supported within the firsttubular, and the second tubular having a lower end within the firsttubular. The method generally includes connecting the downhole tool to awellbore transport member. The downhole tool and the wellbore transportmember are inserted inside of the wellbore containing the first andsecond tubulars. The downhole tool is thus moved with the wellboretransport member past the lower end of the second tubular. The downholetool is moved with the wellbore transport member within a portion of thefirst tubular that does not contain the second tubular. Setting slips onthe downhole tool are expanded to engage an inner wall of the firsttubular. The downhole tool is disconnected from the wellbore transportmember. A whipstock assembly is provided for the downhole tool and aportion of the whipstock assembly is expanded to engage the inner wallof the first tubular. The setting slips on the downhole tool areretracted from the inner wall of the first tubular. The downhole tool isretrieved from the wellbore.

The downhole tool for operation within the borehole generally includes awhipstock having a radially expandable portion moveable between a setposition for engaging an inner surface of the borehole and an unsetposition radially offset from the inner surface of the borehole. Asupport member is secured to the whipstock that has a radial expandableslip assembly movable to a set position for engaging the inner surfaceof the borehole to secure the support member and the whipstock withrespect to the borehole. The support member is also movable to an unsetposition such that the slips are disengaged from the inner surface ofthe borehole to allow the retrievable tool to be movable within theborehole. Furthermore, there is an interconnection to a boreholetransport member.

The downhole tool may further include a body portion. A first slidingmember is slidably secured to the body portion and is movable between aset position and an unset position. A second sliding member is slidablysecured to the first sliding member and is movable between a setposition and an unset position. At least one slip is slidably secured tothe second sliding member. At least one slip is movable between aradially outwardly set position and a radially inwardly unset position.A first slip member is slidably secured to the slip and is radiallymoveable between the set position and an unset position. A second slipmember is slidably secured to the first slip member and is radiallymovable between a set position and an unset position. The second slipmember is axially spaced from the slip in the set position. The firstand second sliding members are disposed radially between the slips andthe setting member body portion in the set position.

It is an object of the present invention to provide an improvedwhipstock assembly and method.

It is another object of the present invention to provide a whipstockassembly that may be initially positioned and subsequently retrieved bypassing through a small tubular that opens up into a larger tubularwherein a window, such as a casing window, is milled.

A feature of the present invention is an improved expandable andretractable slip assembly.

Another feature of the present invention is an expandable andretractable base portion of the whipstock member.

An advantage of the present invention is the elimination of the need toremove a tubing string before milling a window in a casing string belowthe tubing.

Another advantage of the present invention is ready access to theoriginal casing string after the milling operation.

These and other objects, features, and advantages of the presentinvention will become apparent from the drawings, the descriptions givenherein, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view, partially in section, of an anchorassembly suspended on a setting tool operable to pass through a smallertubing string into a larger diameter casing string;

FIG. 2 is an elevational view, partially in section, showing the settingtool of FIG. 1 being retrieved back through the smaller diameter tubingstring after setting of the anchor assembly within the larger diametercasing string;

FIG. 3 is an elevational view, partially in section, showing adirectional survey tool lowered onto the anchor assembly of FIG. 2 todetermine the radial azimuth of the orientation slot in the riser of theanchor assembly;

FIG. 4 is an elevational view, partially in section, showing an orientedwhipstock assembly being secured to the anchor assembly of FIG. 3;

FIG. 5 is an elevational view, partially in section, showing anenlargement of the working string connection to the whipstock assemblyof FIG. 4;

FIG. 6A is an elevational view showing an enlargement of the hingeportion of the whipstock assembly of FIG. 4 in an unset position forlowering the whipstock assembly through the tubing;

FIG. 6B is an elevational view, partially in section, of the hingeportion of FIG. 6A along the line 6B--6B;

FIG. 6C is an elevational view showing the hinge portion of thewhipstock assembly of FIG. 6A after being placed in a set position;

FIG. 6D is an elevational view, partially in section, of the hingeportion of FIG. 6C along the line 6D--6D;

FIG. 7 is an elevational view, partially in section, of a latchconnection to secure the whipstock assembly to the anchor assembly;

FIG. 8 is an elevational view, partially in section, showing the workingstring being retrieved from the wellbore after setting the whipstockassembly into position for milling;

FIG. 9 is an elevational view, partially in section, showing a startermill having a nose member positioned to engage a ramp on the whipstockassembly for initiating the milling operation to cut a window in thecasing;

FIG. 9A is an elevational view, partially in section, showing thestarter mill of FIG. 9 having partially milled through a portion of thecasing;

FIG. 10 is an elevational view, partially in section, showing anincipient stage of the milling operation after the starter mill of FIG.9 has been removed and prior to replacement thereof by a window mill orother type of mill to complete the milling operation;

FIG. 11 is an elevational view, partially in section, showing a windowmill positioned along the trough or face of the whipstock for continuingthe milling operation along the dotted line projecting the path of themill;

FIG. 12 is an elevational view, partially in section, showing a settingtool attached through a shear stud to the upper portion of the anchorassembly prior to setting the anchor assembly in the casing;

FIG. 13 is an elevational view, partially in section, showing a lowerportion of the anchor assembly with the expanders, slip links, andcasing slips in a collapsed or retracted position;

FIG. 14 is an elevational view, partially in section, showing the upperportion of the set anchor assembly of FIG. 12 with the anchor mandrellocked in position after the stud has been sheared;

FIG. 15 is an elevational view, partially in section, showing the lowerportion of the anchor assembly of FIG. 13 with the expanders, sliplinks, and casing slips in the expanded position to secure the anchorassembly with respect to the casing;

FIG. 16 is a quarter sectional view showing an enlargement of a lowerportion of the anchor assembly with the expanders, slip links, and slipsin a collapsed or retracted position;

FIG. 17 is a quarter sectional view showing the lower portion of theanchor assembly of FIG. 16 with the expanders, slip links, and slips inthe expanded position;

FIG. 18 is an exploded perspective view of the slip links in the lowerportion of the anchor assembly of FIG. 17;

FIG. 19 is an elevational view, partially in section, showing theworking string secured to the whipstock assembly after placing thewhipstock hinge in the unset position during removal from the wellboreupon completion of the whipstock operation;

FIG. 20 is an elevational view, partially in section, showing anenlargement of the working string connection including a grapple forremoval of the whipstock assembly;

FIG. 21 is an elevational view showing the hinge portion of thewhipstock assembly after being returned to the unset position forremoving the whipstock assembly from the wellbore through the tubing;

FIG. 22 is an elevational view, partially in section, of the hingeportion of FIG. 21 along the line 22--22;

FIG. 23 is an elevational view, partially in section, of the whipstockand anchor assembly after the ratchet lock for the anchor mandrel hasbeen released to allow removal of the anchor assembly from the wellborethrough the tubing; and

FIG. 24 is a quarter sectional view of a lower portion of the anchorassembly in a collapsed or retracted position to allow removal of theanchor assembly from the wellbore through the tubing.

While the present invention will be described in connection withpresently preferred embodiments, it will be understood that it is notintended to limit the invention to those embodiments. On the contrary,it is intended to cover all alternatives, modifications, and equivalentsincluded within the spirit of the invention and as defined in theappended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a through tubing whipstock and anchorassembly for milling a window in a wellbore tubular that may be loweredthrough a smaller diameter tubular string and set for performing awhipstock operation within a larger diameter tubular string, and maysubsequently be unset and retrieved from the wellbore through thesmaller diameter tubular string.

By way or example only and not by way of limitation, a whipstockoperation according to a presently preferred embodiment of the inventionmay proceed by first lowering the anchor assembly, that is attached toan electrically activated setting tool, through the bottom of the tubinginto a casing string as schematically indicated in FIG. 1. It will beunderstood that the anchor assembly may also be lowered from a coiledtubing string or work string, then set with a hydraulically activatedsetting tool. After the anchor assembly has been set within the casingstring, the setting tool may be removed as shown in FIG. 2. A surveytool having an orientation lug is then lowered onto a whipstockorientation slot in the anchor assembly for receipt of the orientationlug. The survey tool is releasably supported by the expanded anchorassembly as shown in FIG. 3. After obtaining the orientationinformation, the survey tool is removed from the wellbore and theorientation information from the survey tool is used on the surface toorient the whipstock face with respect to a corresponding orientationlug disposed on the lower portion of the whipstock latch assembly. Inthis manner, the whipstock face will be oriented so that the casingwindow will be milled at the desired radial azimuth of the wellbore. Thewhipstock assembly is then lowered onto the anchor assembly for accurateorientation by the orientation lug and is secured to the anchor assemblyas shown in FIG. 4. The whipstock assembly is set for operation and thework string removed from the borehole as shown in FIG. 8. The millingoperation may proceed as shown generally in FIGS. 9-11 beginning with astarter mill to initiate the milling operation of the casing window.After completing the milling operation and the side track or lateraldirectional drilling operation, the whipstock assembly and anchorassembly may be unlocked from the set position and retrieved from thewellbore as indicated in FIGS. 19-24. Alternatively, the whipstockassembly may be retrieved while the anchor assembly remains secured tothe casing, as explained below.

For convenience of understanding only, descriptive terms such as"upwardly", "downwardly", and the like, may be used in thisspecification to conveniently describe the present invention inassociation with the accompanying drawings. However, it will beunderstood that such terms are used for explanatory purposes only andare not to be construed in any manner as limiting the invention. Thoseskilled in the art will recognize that often the orientation andconfiguration of the equipment described herein may be different fromthat illustrated in the accompanying drawings and that this terminologyis used only for case of understanding the presently preferredembodiments of the present invention. As well, when referring to depthin a wellbore, this will generally mean a length of the wellbore ratherthan a specific elevational depth so that an offset well may have adeeper depth than a straight well even though both end at the sameelevational depth.

Referring now to the drawings, and more particularly to FIG. 1, there isshown a through tubing anchor assembly 10 in accord with the presentinvention. Anchor assembly 10 may be lowered into the casing C, set inwellbore 13, through the tubing T by means of wireline 12 or by means ofa working string as discussed in U.S. application Ser. No. 08/223,704filed Apr. 4, 1994 and incorporated herein by reference. For exampleonly, casing C may be a 7 inch O.D. casing and tubing T may be a 41/2inch O.D. tubular production string.

Wireline 12 may be used to accurately position the depth of anchorassembly 10 within the bore 14 of casing C using collar locator (notshown) and/or other depth control device as is normally utilized alongwith a wireline setting tool WSS. Thus, the depth position for settinganchor assembly 10 may be correlated to the desired formation strata orother desired position in the wellbore in a manner known to thoseskilled in the art so that a side track or lateral drilling operation orother type of drilling operation may proceed along a predeterminedoptimal path. A hydraulic setting tool HSS may also be used as desiredand may be supported by a working string that may include coiled tubingor individual tubulars threadably secured together. In some cases, itmay be necessary to provide a setting tool with a stroke somewhat longerthan may by typical due to the need for the slips of anchor assembly 10to expand radially outwardly from the anchor by a distance that issignificantly greater than is common in the standard full bore entryoperation.

Wireline setting tool WSS may be adapted for attachment to anchorassembly 10 by means of an adaptor kit that includes adaptor settingsleeve 16, mandrel adaptor 18, and shear stud 20 as schematicallyindicated in FIG. 1. As schematically indicated more clearly in theenlarged view of FIG. 12, anchor mandrel 22 is secured to mandreladaptor 18 by means of shear stud 20. The entire weight of anchor 10 issupported by shear stud 20 below wireline setting tool WSS. Thus, whenshear stud 20 shears into two pieces at weak link portion 21 due to apredetermined separation force applied thereto, setting tool WSS willthen be separate from anchor 10 and may be retrieved to the surface withwireline 12.

Prior to actuating wireline setting tool WSS, shear stud 20 has upperand lower threaded portions spaced apart on either end from weak linkportion 21 as shown in FIG. 12. Upper and lower slips 24 and 26,respectively, are in the unset, collapsed, or retracted position toallow anchor assembly 10 to be lowered through smaller diameter tubing Tinto larger diameter casing C as shown in FIG. 13. Thus, the outerdiameter of anchor assembly 10 is smaller than the smallest innerdiameter portion of tubing T by a clearance factor that may typically beat least 1/8 of an inch. FIG. 13 shows the lower portion of the unsetanchor assembly 12 in a detailed view. It will be noted that thesmoother surfaces of anchor assembly 10 preferably have the largestouter diameter of the anchor assembly so as to substantially preventsharper elements, such as the metallic slips, from engaging the tubingor casing prior to reaching the desired depth of setting.

Anchor mandrel 22 threadably secures to and extends from shear stud 20.Anchor mandrel extends downwardly through anchor sleeve 28, throughupper expander 30, through upper and lower slips 24 and 26, and to lowerexpander 32 where it is threadably secured with threaded connection 34.

As shown in FIG. 12, adaptor setting sleeve 16 abuts shoulder 36 ofupper bushing 38 of anchor 10. Thus, shoulder 36 transmits any relativedownwardly directed force applied by adaptor setting sleeve 16 to upperbushing 38. Furthermore, any downwardly directed force applied byadaptor setting sleeve 16 to upper bushing 38 is also applied to upperexpander 30 that is fixable secured to upper bushing 38 by means ofanchor sleeve 28 that is threadably interconnected between upper bushing38 and upper expander 30.

Prior to detonation of the electric blasting cap that will initiate thesetting process, the anchor assembly will typically be lowered below thesetting point, if wellbore conditions allow, to check collars foraccurate depth control. The anchor assembly will then be pulled upwardlywith a constant stretch in the wireline cable and stopped at the desiredposition with the relevant lengths of the anchor assembly, setting tool,and whipstock having been used to calculate that the anchor assembly ispositioned correctly for the exact depth, within inches, for the desiredposition of the casing window.

Upon detonation of a controlled and comparatively slow burning explosivewithin setting tool WSS, the setting tool begins to operate. The typicalsequence of setting can be monitored on the wireline weight indicator atthe surface assuming the depth and deviation of the wellbore is not toogreat. The line tension typically increases slightly after the explosivecharge is electrically detonated and then, after about 5-10 seconds,suddenly drops off significantly when the weight of the anchor isdetached from the setting tool by shearing of shear stud 20.

Essentially, setting tool WSS produces a relative downward movement ofadaptor sleeve 16 with respect to anchor mandrel 22. Mandrel 22 issecured to lower expander 32. Adaptor sleeve 16 applies a downwardlydirected force on upper expander 30 which is relatively movable withrespect to lower expander 32. Therefore, upper expander 30 and lowerexpander 32 are forced to move relatively toward each other by operationof setting tool WSS. As lower expander 32 and upper expander 30 moverelatively toward each other, upper and lower slips 24 and 36 are forcedradially outwardly in a manner to be discussed hereinafter to engagecasing C as shown generally in FIG. 2, and shown in an enlarged view inFIG. 15. The setting tool operation is completed when shear pin 20breaks at weak point 21 as shown most clearly in FIG. 14. After shearpin 20 breaks to end the setting tool process, setting tool WSS or HSSmay be retrieved upwardly towards the surface in the direction 75' asindicated in FIG. 2 through tubing T.

It will be observed by comparison between FIG. 12 and FIG. 14 thatanchor mandrel 22 has moved upwardly towards orientation mandrel 40during the setting process. As well, shear stud 20 is broken or shearedat weak link 21 with a predetermined force that assures that the settingoperation is completed. Upper and lower slips 24 and 26, respectfully,remain engaged against casing C after shearing of shear stud 20 becauseanchor mandrel 22 is secured in place by flexible ratchet ring 42.Flexible ratchet ring 42 thus engages mandrel ratchets 44 to preventmandrel 22 from moving downwardly, with respect to upper and lower slips24 and 26, after shear stud 20 is sheared so that the slips remainengaged with casing C.

Upper and lower opposed slips 24 and 26, best seen in FIG. 15, areindependently radially movable outwardly and inwardly. The slips aresecured against casing C by means of relatively sliding members,discussed hereinafter, that slide upon each other in response to therelative movement of lower expander 32 in the direction of upperexpander 30, to thereby force upper and lower slips 24 and 26 radiallyoutwardly.

The uppermost and lowermost relatively sliding members will be referredto as upper and lower outer expanders, 46 and 48, respectively. Adjacentto these are upper and lower inner expanders, 50 and 52, respectively.Upper and lower inner expanders 50 and 52 are slidably secured to upperand lower slips 24 and 26, respectively, by a dovetail slotted keyinterconnection. Specifically, the relative slidable interconnectionsbetween each of the expanders as well as between the outer expanders andthe slips may typically include two keys each having dovetail profiledcross sections. The keys are secured as with screws to the lower orradially inwardly side of each expander and each slip. The relativeprofile of the dovetail keyed slot interconnection is functionallysimilar to that of the interconnection between the slip links shown inFIG. 18 that is discussed hereinafter. The dovetail keys are securedwithin the upper and lower slots 53 and 55 shown in FIG. 13,respectively, that are provided between the expander and slip elements.The dovetail profile of mating keys and slots in combination with limitpins 74 within the limiting slots described below secure the expandersand slips together to thereby prevent relative disengagement of thesecomponents from each other. The dovetail keyed slot interconnection alsoallows relative substantially longitudinal or axial sliding movementbetween these components while preventing relative rotation of theexpanders and slips about anchor 10 that might disturb the azimuthalorientation of the whipstock assembly.

Between upper and lower slips 24 and 26 are sets of respective sliplinks that are numbered in FIG. 15 where both a cross-sectional view anda perspective view of the slip links is available. Upper and lower innerslip links 54 and 56 are each slidably secured to slip cage 58. Upperand lower middle slip link 60 and 62, respectively, are slidably securedto the respective inner slip links. Upper and lower outer slip links 64and 66, respectively, are slidably secured between the respectivemiddlemost slip links and the respective upper and lower slips 24 and26. Since they are all interconnected to the slip cage 50, the sliplinks assure substantively uniform radial outward movement of each ofthe circumferentially spaced upper slips 24 or lower slips 26, Sincethey are all interconnected to the slip case 56, the slip links ensuresubstantially uniform radial outward movement of each of thecircumferentially spaced upper slips 24 or lower slips 26.

Due to their separate connection to slip cage 58, the upper and lowerslip assemblies, that include the upper and lower expanders, the upperand lower slip links, and the separate upper and lower slips, functionsubstantially independently from each other during setting and unsettingfunctions. Thus, lower slips 26 and upper slips 24 engage and disengagecasing C independently from each other as lower expander 32 and upperexpander 30 move toward or away from each other. This feature results inthe reliable settings of the anchor slips such that the anchor centralaxis remains aligned with the axis of the casing. The independentdisengagement of the slips also allows for the unsetting and retrievalof the anchor, as explained hereafter.

Referring now to FIGS. 16-18, further details of the lower slipcomponents including lower expanders, slip links, and slips aredisclosed. It will be understood that the construction of upper slipassembly components including expanders, slip links, sliding surfaces,and slips essentially mirrors the construction of the lower slipassembly components expanders, slip links, sliding surfaces and slips.For convenience, discussion of the lower slip assembly components thusalso applies to the upper slip assembly components unless otherwisenoted. FIG. 16 shows the lower slip assembly components in the unset orretracted position while FIG. 17 shows the lower slip engagementcomponents in the set, position. FIG. 18 discloses the configuration ofthe slip links.

The expanders, slip links, and slips slide with respect to each other onsurfaces that are angled or inclined with respect to the anchor centerline 68 so that as lower expander 32 and upper expander 30 move towardseach other, the expanders, slip links, and slips are wedged or urgedradially outwardly towards casing C. The magnitude of the angle of therelative sliding surfaces of the upper and lower slip assemblies withrespect to the anchor tool axis or centerline 68 is the same in thecross-section that includes the centerline 68 as shown FIG. 17 and FIG.18. However, the orientation of measurement of the magnitude of theangle of the upper assembly sliding surfaces is taken from the axisbeginning 180° out of phase as compared with the lower assembly slidingsurfaces.

The construction of the inclined surfaces between the expanders isdiscussed in application Ser. No. 08/223,704 and is therefore onlybriefly reviewed here. The inclined, curved surfaces on the expandersare substantially parallel for each axially neighboring expander on thesame slip assembly and are preferably of a continuous uniform radius orcurvature. In other words, a cross-section perpendicular to anchor axis68 through corresponding portions of axially neighboring expanders willshow curved but parallel relative sliding surfaces. Verticalcross-sections of axially neighboring expanders as shown in FIG. 16 andFIG. 17 will show substantially straight and parallel relative slidingsurfaces. See, for instance, sliding surfaces 82 and 84.

In cross-sections perpendicular to the central axis 68 of the tool, thecircumferentially spaced sliding surfaces between the expanders liealong the circumference of a circle, and are not conical. Such across-section perpendicular to the anchor axis shows these surfaceslying on rounded lobes that would connect, for instance, in triangularfashion the three sets of circumferentially spaced lower slipassemblies. Because the expanders absorb large radial forces duringsetting and while the anchor is set, the expanders preferablycollectively have a surface area that substantially extends around thecircumference of anchor assembly 10 when in the collapsed position tominimize the radial force applied per square inch to the inner and outersurfaces of the expanders.

Lower expander inclined surface 70 on lower expander 32 engages matingouter expander surface 72 on outer expander 48. Limit groove 74 isdisposed within outer expander surface 72 and, in conjunction with limitpin 73, limits the extent of sliding movement of outer expander 48.Limit groove 74 may be designed to limit movement of the outer expanderboth in the collapsed and expanded positions, as desired, by means ofexpansion limit shoulder 76 and collapsed limit shoulder 78.

Aperture 80 is provided through outer expander 48 to be in communicationwith limit groove 74 as a convenience during assembly for insertinglimit pin 73. Likewise, apertures 81 and 83 are provided in innerexpander 52 and lower slips 26 for similar assembly purposes.

Mating sliding surfaces, indicated generally at 82, are similarlyprovided between outer expander 48 and inner expander 52. As well,mating sliding surfaces, indicated generally at 84, are provided betweeninner expander 52 and lower slips 26.

Separate from and circumferentially spaced on either side of therespective limit grooves 74, 82, and 84 in the expander and slipelements are the dovetail keyed slots discussed hereinbefore.Representative dovetail slots 53 and 55 are shown in FIG. 13. Thedovetail keyed slots also have sliding surfaces that correspond inorientation to the mating inclined surfaces disposed between theexpanders.

The dovetail keyed slots and limit grooves in the slip links areessentially combined, as best shown in FIG. 17. In outer slip link 66,for instance, set screw 86 fixably secures limit pin 88 within outerslip link 66 through dovetail key 90. Dovetail key 90 interconnects withdovetail slot 92 in middle slip link 62 to slidably secure outer sliplink 66 to middle slip link 62. Limit groove 94 is disposed withindovetail slot 92 to receive limit pin 88. Limit pin 88 and limit groove94 cooperate to limit the extent of respective sliding movement betweenouter slip link 66 and middle slip link 62 as desired.

Limit pin 96 is secured to lower slip 26 by set screw 98 and is receivedinto limit groove 100 to limit respective sliding movement between outerslip link 66 and lower slips 26. It will be noted that in thisembodiment of the present invention, outer slip link 66 includes twodovetail keys, i.e. upper and lower dovetail keys 90 and 102,respectively. Inner slip link 56 and middle slip link 62 each have onlyone dovetail key. Thus, dovetail key 104 and dovetail key 106 aredisposed on inner slip link 56 and middle slip link 62, respectively.Inner slip link 56 and middle slip link 62 also include dovetail slots108 and 92, respectively whereas outer slip link has no dovetail slot.It should be understood that other configurations for placement andreceipt of the dovetail slots and keys could be made.

Each limit groove, such as limit groove 110, includes expanded andcollapsed position limit shoulders, such as respective limit shoulders112 and 114, to thereby limit the relative movement by the slip assemblybetween the expanded and collapsed position. For this purpose, the limitshoulders engage a corresponding limit pin, such as limit pin 116, tothereby limit the extent of sliding movement between slip link 62 andslip link 56. Finally, inner slip link 56 is secured to cage 58 viadovetail key 104. Relative sliding movement between slip link 56 andcage 58 is limited by limit pin 118 (see FIGS. 16 and 17) that moveswithin limit groove 120.

Relative sliding between the cage, slip links, and the slips occursalong inclined surfaces that, in the presently preferred embodiment,have a slip link inclination that is substantially orthogonal to theinclination of sliding surfaces between the expander members and theslips. The expander inclination is shown, for example, in thecross-section of FIG. 16 and FIG. 17. Because the angle of inclinationbetween the axis or centerline 68 of anchor assembly 10 and the expanderinclination is much smaller than that of the slip link inclination, theexpanders tend to absorb most of the forces that cause the slips toengage against casing C. The radial setting forces are quite large andare therefore better absorbed by the larger surface areas of theexpanders as compared to the slip links. The expanders are disposedradially inwardly between the slips and the anchor assembly 10 whenanchor assembly 10 is set. For instance, when anchor assembly 10 is set,lower expander 32 is beneath and radially inwardly with respect to outerexpander 48, inner expander 52 and slip 26 to thereby support the radialforces.

Because the forces to be absorbed by the slip links tend to be axiallydirected rather than radially directed, the sliding surfaces of the sliplinks may be conveniently substantially flat rather than radiused. Theslip links may be axially spaced from the slips whether in the set orunset position because they do not transmit substantial radial forces.The side portions of all the dovetail keys and slots on all slipassembly components including cage 58, the slip links, upper and lowerslips 24 and 26, and the expander members, tend to absorb most of therotational forces that act on anchor assembly 12 to prevent rotationthereof with respect to casing C. It is necessary to avoid rotation ofanchor assembly 12 during the milling and drilling operation that willresult in torque and weight being applied to anchor assembly 10.

The sliding surfaces of the lower slip links and related surfaces oncage 58 and lower slips 26 are preferably parallel to each other and, inthe presently preferred embodiment, include surfaces on the dovetailslots and keys, as discussed hereinbefore, as well as surfaces adjacentthereto. By way of example, such surfaces also include surfaces 122 oneither side or dovetail slot 92 on middle slip link 62 that aresubstantially parallel to sliding surfaces on the bottom of dovetailslot 92. Referring to FIG. 24, such relative mating surfaces alsoinclude dovetail keyed slot engagement surfaces such as mating surfaces124 between lower slip 26 and outer slip link 66, mating surfaces 126between outer slip link 66 and middle slip link 62, mating surfaces 128between middle slip link 62 and inner slip link 56, and mating surfaces130 between inner slip link 56 and cage 58.

As shown in FIG. 2, after the anchor assembly 10 is set and the settingtool removed from the wellbore, the orientation mandrel 40 secured tothe upper portion of anchor 10 is exposed. As shown in the enlarged viewof FIG. 14, orientation mandrel is fixably secured to release sleeve 132via threaded connection 134 to butt against shoulder 36 of upper bushing38. As will be noted, release sleeve 132 is prevented from rotation byset screw 136 and slot 138. Set screw 136 extends into slot 138 throughupper bushing 38, that is screwed down to butt against shoulder 140 onanchor sleeve 28 to prevent further rotation thereof. Thus, theorientation mandrel cannot rotate after the anchor assembly is set.

The orientation mandrel 40 includes an orientation slot 142 into whichwill be received and orientation lug as discussed hereinafter. As well,an inclined guide surface 144 along the upper portion of orientationmandrel 40 slopes downwardly toward orientation slot 142 to guide theorientation lug into the orientation slot 142. Retention groove 198cooperates with a latch mechanism to secure the whipstock assembly toanchor assembly 10 as discussed hereinafter.

Referring to FIG. 3, directional survey tool 146 is lowered by wireline12 onto orientation mandrel 40. Directional survey tool 146 includes ansurvey sleeve 148 that telescopes over orientation mandrel 40 asdirectional survey tool 146 descends through casing C. Orientation lug150 is fixably secured within survey sleeve 148. Thus, as survey sleeve148 descends over orientation mandrel 40, orientation lug 150 engagesguide surface 144 that guides orientation lug 150 into orientation slot142. Although directional survey tool 146 preferably includecentralizers 152, the centralizers are mounted in such a way that thedirectional survey tool is substantially free to rotate to alloworientation lug 150 to be guided into orientation slot 142.

It will be noted that several features guide survey sleeve 148 overorientation mandrel 40 to prevent it from becoming cocked or otherwiseimproperly engaging orientation mandrel 40. This is particularlyimportant for operation in a deviated well bore. Due to the fact that itmay be impossible to immediately ascertain from the surface whethersurvey sleeve 148 correctly engages orientation mandrel 40, it isdesirable to provide means to ensure proper engagement. Various meansare thus used for this purpose, including centralizers 152 thatcentralize directional survey tool 146 within casing C to thereby guidesurvey sleeve 148 over orientation mandrel 40. As well, beveled end 152or survey sleeve and beveled end 154 of orientation mandrel 40 engage toguide survey sleeve 148 over orientation mandrel 40. After directionalsurvey tool 146 collects the information as to the radial azimuthalorientation of orientation slot 142, the directional survey tool isremoved from the hole by wireline 12.

The directional survey tool provides information as to the azimuthalorientation of orientation slot 142. With this information, the face ofthe whipstock assembly can be correctly oriented on the surface withrespect to a second orientation lug that is provided on the whipstockassembly. The manner or making this surface orientation adjustmentinvolves separating and reconnecting a spline-groove connection betweenthe whipstock face and the whipstock alignment lug based on the surveyinformation that provides the azimuth of orientation slot 142. Onceadjusted, the spline-groove connection is locked together. The number ofsplines and grooves determines the resolution of the accuracy to whichthe whipstock face can be oriented. For instance, 72 orientationpositions would provide a 5° resolution.

It will be understood that whipstock assembly 160 is properly orientedat the surface so that when alignment lug 164 engages orientation slot142 as shown in FIG. 4, then whipstock face 162 is oriented to guide amill, as discussed hereinafter, in the desired azimuthal radialdirection for the casing window. The spline-groove connection may becontained in quick change connection 166. Whipstock face 162 cannotrotate with respect to whipstock alignment lug 164 once quick changeconnection 166 is made up. Thus, after the whipstock assemblyorientation is accomplished on the surface, then whipstock assembly 160is lowered through the bottom of tubing T into casing C using workingstring 168.

Whipstock assembly 160 further includes hinge assembly 170 that, in theset position, supports the base portion of whipstock assembly 160 withincasing C, as discussed hereinafter. In the unset position, hingeassembly 170 streamlines the profile of whipstock assembly 160 so thatit will have an outer diameter smaller than the inner diameter of tubingT.

Centralizer 172 is mounted above whipstock orientation sleeve 174 tocentralize and therefore guide whipstock orientation sleeve 174 overorientation mandrel 40 in telescoping relationship as discussedhereinbefore with regard to directional survey tool 146. Whipstockorientation sleeve 174 is very similar to and, for engagement purposes,substantially identical to survey tool orientation sleeve 148.Centralizer 172 is connected to centralizer sub body 176 by means ofupper and lower rotatable rings 178 so as not to restrict free rotationof whipstock assembly 160 in casing C. Thus, as whipstock alignment lug164 engages inclined guide surface 144 on orientation mandrel 40,whipstock assembly 160 is substantially free to rotate in casing C untilalignment lug 164 is guided to slide into orientation slot 142. Theweight of whipstock assembly 160 and workstring 168 produces aconsiderable torque for rotating whipstock assembly 160 to therebyposition whipstock alignment lug 164 into orientation slot 142 aswhipstock alignment lug 164 slides downwardly on inclined guide surface144.

Whipstock assembly 160 may be secured to working string 168 with adaptor180 that stabs into adapter receiving hole 181 through the top 183 ofwhipstock assembly 160. Adaptor 180 includes at least one shear pin 182as best shown in the enlarged view of FIG. 5. Shear pin 182 supports theentire weight of whipstock assembly 160 as the assembly is lowered intothe wellbore. Shear pin 182 is installed into annular groove 184 thatencircles adaptor 180 through shear pin threaded hole 186 in whipstockassembly 160. Thus, whipstock assembly 160 may rotate with respect toadaptor 180 and working string 168 as shear pin 182 moves in annulargroove 184 for orientation of whipstock assembly 160.

After securing whipstock assembly 160 to anchor assembly 10 and settingwhipstock hinge assembly 170 as discussed hereinafter, working string168 may be removed by shearing shear pin 182 with an upward pull.Adaptor end surface 187 may be used to apply downwardly directedpressure on whipstock assembly 160 for attaching anchor assembly 10thereto and also for setting hinge assembly 170. Adaptor receiving hole181 also includes retrieving threads 188 to retrieve whipstock assembly160 as discussed hereinafter. The same adaptor 180 may be fitted withretrieval grapple 190, as best shown in FIG. 20.

FIG. 7 discloses an interconnection assembly 192 in accord with thepresently preferred embodiment for interconnecting whipstock assembly160 with anchor assembly 10. Individual circumferentially spaced fingerssuch as finger 194 are moved upwardly and flexed outwardly fromorientation mandrel 40 of anchor assembly 10 as whipstock assembly 160is lowered thereon until inward projection 196 on the end of each finger194 engages retention groove 198 on orientation mandrel 40. Upwardmovement of whipstock assembly 160 moves finger support 200 that isdisposed on end portion 202 of whipstock orientation sleeve 174 adjacentinward projections 196 in retention groove 198 to thereby interconnectwhipstock assembly 160 with anchor assembly 10. Due to pins, such as pin204 that is secured to end portion 202 and extends into groove 206, endportion 202 may move downwardly with respect to finger 194 to provideadditional support for anchor sleeve 174 as finger supports 200 alsoengage retention groove 196. When anchor assembly 160 is liftedupwardly, pins 204 releasably support the tension required for unsettingand retrieving anchor assembly 10.

FIG. 8 shows hinge assembly 170 in the set position. The process ofsetting hinge assembly 170 is illustrated in FIGS. 6A-6D that provideenlarged views of hinge assembly 170. FIG. 6A and FIG. 6B show hingeassembly 170 in the unset position. FIG. 6C and FIG. 6D show hingeassembly 170 in the set position.

In general terms, when weight is applied to whipstock assembly 160 bymeans of working string 168, hinge block 208 rotates with respect toupper and lower offset hinge pins 210 and 212, respectively, therebyplacing hinge assembly 170 in the set position.

Hinge block 208 is secured between the forks of both upper fork 214 andlower fork 216. Upper offset hinge pin 210 extends through upper fork214 and hinge block 208 to thereby rotatably secure hinge block 208 forrelative rotation within upper fork 214. Lower offset hinge pin 212extends through lower fork 216 and hinge block 208 for relative rotationwithin lower fork 216. Shear pin 217 maintains hinge assembly 170 in theunset position to maintain the small diameter unset position ofwhipstock assembly 160 for moving downwardly through smaller diametertubing T. Weight applied to hinge assembly 170 by working string 168shears shear pin 217 and moves hinge assembly to the set position.

Lower fork 216 contains therein locking means to lock hinge assembly 170in the set position. This locking mechanism includes two spring-loadedshearable pin assemblies 218 and 220 for engaging corresponding locksockets 222 and 224, respectively, that are disposed on opposite sidesof hinge block 208. Thus, as hinge block 208 rotates relative to upperand lower forks 214 and 216, respectively, from the unset position asshown in FIG. 6A to the set position as shown in FIG. 6C, spring loadedshear pins 226 and 228 engage respective lock sockets 222 and 224 tothereby lock hinge assembly 170 in the set position, as shown mostclearly in FIG. 6D. Lock sockets 222 and 224 are preferably somewhatextended or elongate to be larger than the spring loaded shear pins sothat hinge assembly 160 can adjust to a certain extent for hole sizewhile in the locked position. Springs 223 and 225 provide the biasingmeans for the spring loaded shear pins.

Upper fork 214 rotates in the direction or upper rotation directionarrow 232 to move hinge assembly 170 to the set position from the unsetposition. Upper limit pin 230 extends into hinge block 208 and abuts thelower adjacent end of upper fork 214 to prevent relative rotation aroundupper offset hinge pin 210 in the opposite direction, when lockingassembly 170 is in the unset position.

Lower fork 216 rotates in the direction of lower rotation directionarrow 236 to move hinge assembly 170 to the set position from the unsetposition. Similarly, lower limit pin 234 extends into hinge block 208and abuts the upper adjacent end of lower fork 216 to prevent relativerotation around lower offset hinge pin 212 in a direction opposite thatof lower direction arrow 236 when locking assembly 170 is in the unsetposition.

To effect retrieval of whipstock assembly 160, shearable ends 238 and240 of respective spring loaded shear pins 226 and 228 are sheared off,in a manner discussed hereinafter. In some cases, it may be desired touse a screw (not shown) extending through each of holes 242 and 244 toengage the respective spring loaded pins to prevent actuation duringtransport until final assembly for operation.

Referring now to FIG. 8, after placing hinge assembly 170 in the setposition, working string 168 may be retrieved. Setting of hinge assembly170 expands base region 248 of whipstock member 246 to support whipstockmember 246 during the milling operation. Whipstock member 246 may, ifdesired, have a casing engaging contour 250 and another casing engagingcontour 252 that engage casing C over a longer length when hingeassembly 170 is set to thereby better more evenly disperse milling anddrilling forces applied thereto. Whipstock face 254 is preferablyconcave for receiving and guiding a window mill 266.

In FIG. 9, starter mill 256 is shown. A stater mill may preferably beused to initiate the milling operation. Starter mill 256 includes a noseor pilot portion 258 to engage ramp 259 that preferably includes rampextension 260. Nose or pilot portion 258 and ramp extension or pilot lug260 cooperate to position mill blades 262 against casing C and initiatecutting the casing window as shown in FIG. 9a. Otherwise, the mill mayhave a tendency to mill out the whipstock member 246 without openingcasing window 264 as desired. As well, mill blades 262 are not as deepas mill blades used with a full bore mill operation because the millmust have an O.D. smaller than the I.D. of the smallest restriction intubing string T. Nose portion 258 may be fixed or rotatable with respectto mill blades 262 as desired to eliminate wear on nose portion 258.Ramp extension member 260 may be partially milled off during the millingoperation. Nose portion 258 will preferably be designed to wedge andthereby stop milling once the cutting of casing window is successfullyinitiated.

As indicated in FIGS. 10 and 11, the starter mill is preferably removedafter the milling operation is initiated to penetrate the casing and isreplaced with a window mill 266 to continue the milling operation asindicated in dashed lines in FIG. 11 as projected wellbore 268 and millassembly 270. Various other mills may be used as wellbore 268 isdeepened, including string mills or tapered mills to clean up casingwindow 264. After the wellbore is sufficiently deep, a conventionalbottom hole assembly may be provided on working string 168 to deepenwellbore 268 to the desired bottom or TD 271.

After the new wellbore is completed, it may be desirable to be able toremove the whipstock assembly from the original borehole. FIG. 20 showsan enlargement of the assembly used to stab into the whipstock assemblyshown in FIG. 19. To retrieve whipstock assembly 160, retrieval grapple190 is secured to adaptor 180 and adaptor 180 is secured to the end ofworking string 168, run into casing C, and stabbed into adaptorreceiving hole 181 in whipstock top 183. Recess 272 in adaptor 180allows grapple blade portion 274 to engage retrieving threads 188 asadaptor 180 moves downwardly. Subsequently, as adaptor 180 is pulledupwardly, the larger diameter of backup sockets 276 preventdisengagement of grapple blade portion 274 and retrieving threads 188.Retrieval grapple 190 moves relatively with respect to adaptor 180 dueto grapple pins 280 moving in slots 282. The arrangement of grapple pins280 within slots 282 also maintains grapple blade portion 274 innonrotational relationship with backup sockets 276. Bottom shoulder 278pulls upwardly to engage the bottom of retrieval grapple 190 while pins280 prevent further relative movement between adapter 180 and pins 280.Thus, working string 168 is secured to whipstock assembly 160 toretrieve it from casing C with an upwardly pull as discussedhereinafter. If for any reason whipstock assembly 160 cannot beretrieved, the left-hand retrieving threads 188 permit disengagement ofadaptor 180 from whipstock assembly 160 upon application of right-handtorque to the workstring 168.

Referring now to FIGS. 21 and 22, the process for placing hinge assembly170 in the unset position to thereby allow whipstock assembly 160 to beremoved from the wellbore through a smaller diameter tubing T isillustrated. Thus, pulling upwardly on hinge assembly 170 causesshearable ends 238 and 240 of spring loaded shear pins 226 and 228 toshear off.

It will be noted that shear pin 182 discussed hereinabove and shown inFIG. 5 is used to separate working string 168 from whipstock assembly160 after initially placing hinge assembly 170 in the set position.Shear pin 182 must therefore be sized to shear with an upward pull ortension less than the upward pull or tension required to shear shearableends 238 and 249 to place hinge assembly 170 back into the unsetposition for retrieval from the wellbore through the smaller diametertubing T. Upper and lower unsetting direction arrows 284 and 286indicate the relative rotation direction of upper fork 214 around upperoffset hinge pin 210 and lower fork 216 around lower offset hinge pin212. Limit pins 230 and 234 prevent further rotation in this directionas discussed hereinbefore. In this manner, the outer diameter ofwhipstock assembly 160 is contracted to a smaller diameter that allowsit to fit through a smaller diameter tubing T.

Referring now to FIG. 23, the procedure for unsetting anchor assembly 10is illustrated. Additional upward pull applied in the direction of arrow288 on whipstock assembly 170 is also effectively applied to anchorassembly 10 through interconnection assembly 192. More specifically, theupward pull creates an upwardly directed force acting acting onorientation mandrel 40 to which interconnection assembly 192 is securedby means of fingers 194 having inward projections 196 that engageretention groove 198.

This upward force on orientation mandrel 40 causes ratchet lock assembly300 to release. FIG. 14 shows ratchet lock assembly 300 in the lockedposition after setting, while FIG. 23 shows ratchet lock assembly 300after release has been effected. Operation of ratchet lock assembly 300is similar to that of an exemplary ratchet release system shown in U.S.Pat. No. 4,898,245 that is incorporated herein by reference.

Releasable ratchet lock assembly includes flexible ratchet ring 42 whichengages outer ring 302. Lock ring 308 surrounds outer ring 302. Shearscrew 304 secures releasing sleeve 134 in its axial position withrespect to upper bushing 38. Lock ring 308 is prevented from movingdownwardly, or axially away from upper bushing 38, by ledge 310. Lockring 308 engages groove 312 in outer ring 302 to thereby prevent axiallydownward movement away from upper bushing 38 of flexible ratchet ring42, thereby locking anchor mandrel 22 in fixed axial position withrespect to upper bushing 38. However, as orientation mandrel 40 ispulled upwardly under sufficient tension, then shear screw 304 issheared and release sleeve 132 is free to move axially towards upperbushing 38. This causes support wall 306 on the end of release sleeve132 to move upwardly and allow lock ring 308 to expand radiallyoutwardly. Without lock ring 308 to prevent axially downward movement ofsegmented ratchet ring 42, anchor mandrel 22 is free to move downwardlyto release the setting tension forces acting on it. With anchor mandrel22 free to move, upper expander 30 may now move away from lower expander32 to unset the upper and lower slip assemblies.

Release sleeve 132 moves upwardly in response to upward force applied byworking string 168 until it engages lower shoulder 314 of upper bushing38. Referring to FIG. 15, upwardly directed force is applied to upperexpander 30 through anchor sleeve 28. Relative sliding, in a directionopposite of movement caused by the setting operation, between upper slipassembly components including the upper expanders and upper slip linkscauses upper slip 24 to move radially inwardly. As discussedhereinbefore, the use of slip cage 58 slidably secured to anchor mandrel22 allows the upper slip 24 to move independently of opposing lower slip26.

Continued upwardly directed force on cage 58 produces a radiallyinwardly directed force on the lower slip assembly components to releaselower slips 26. Gravity and momentum forces acting on mandrel 22 andlower expander 32 also cause lower expander 32 to move relatively awayfrom upper expander 30 to release lower slips 26. Thus, slip assemblycomponents contract to the position shown in FIGS. 13 and 24. With theouter diameter of anchor 10 contracted to the same as the original outerdiameter, anchor 10 can now move through the smaller inner diameter oftubing T. Since whipstock assembly 160 and anchor assembly 10 aresecured together by interconnection 192 as shown in FIG. 7, whipstock160 and anchor 10 can now be simultaneously removed from casing Cthrough tubing T.

It should be understood that the whipstock assembly 160 mayalternatively be retrieved to the surface while leaving the anchorassembly 10 secured to the casing C. For this embodiment, the shear pin204 is sized to shear prior to pin 304. Upward tension on orientationsleeve 174 thus shears pin 204 (see FIG. 23) allowing the upper surface197 on finger supports 200 to engage the mating downwardly projectingsurface 199 on fingers 194. This movement releases the finger 194 toflex outward, thereby releasing the orientation sleeve 174 from themandrel 40. If the anchor is to be retrieved with the whipstockassembly, the pin 204 is sized to be stronger than pin 304 in theanchor. In this case, pin 304 will shear while pin 204 remains intact,allowing the anchor to be retrieved with the whipstock.

While the foregoing is the presently preferred embodiment of the presentinvention, numerous changes could be made as desired. For instance, ifdesired, a setting mechanism such as a hydraulic or mechanical settingmechanism could be built into the anchor. Also, a whipstock assemblythat includes an anchor could be set with a working string. If desired,whipstock assembly 160 could be removable from mandrel 40 and anchorassembly could be separately retrieved with grapple thread 316 as shownin FIG. 12. The relative angles or the sliding surfaces may be changedas desired. Additional sliding surfaces may be added or removed toeither extend or decrease the expansion range of the slips of anchorassembly 10.

Typically, the range of difference between the outer diameter of theinner tubular, such as tubing string T, and inner diameter of the outertubular, such as casing C, will be at least more than about 1/2 to oneinch. The difference in outer diameter of 41/2 inch tubing and innerdiameter of 7 inch casing is about 11/2 inches. However, the tool mustexpand from the inner diameter of the inner tubular which, for 41/2 inchtubing, may be about 33/4 inches depending on the weight. Thus, theexpansion required for that operation is about 21/4 inches. This is muchgreater than the more typical slip assembly expansion required for fullbore operation, which may be in the range of about 1/4 to 3/8 inches.

It will be noted that the anchor assembly 10 and whipstock assembly 160require, in the presently preferred embodiment, five shear members, orsets of shear members, for operation. The order of shearing is (1) shearstud 20, (2) shear pin 217, (3) shear pin 182, (4) shearable ends 238and 240, and (5) shear screw 304. The final three shear members requirean upwardly axial pull for shearing and therefore must be sized so thatincreasingly larger upwardly axial pulls are required to operate in thedesired sequential order.

The foregoing disclosure and description of the invention isillustrative and explanatory thereof. It will appreciated by thoseskilled in the art that various changes in the size, shape andmaterials, as well as in the details of the illustrated construction orcombinations of features of the various anchor and whipstock elementsmay be made without departing from the spirit of the invention.

What is claimed is:
 1. A method for cutting a window at a window depthin a first tubular disposed in a wellbore, .Iadd.at least .Iaddend.aportion of said first tubular .[.containing therein.]. .Iadd.positionedaxially below .Iaddend.a second tubular having .[.a.]. .Iadd.an interior.Iaddend.diameter .Iadd.and an exterior diameter .Iaddend.less than.Iadd.an interior diameter of .Iaddend.said first tubular, said secondtubular terminating at a lower end, said lower end being disposed at atermination depth in said wellbore less than said window depth, .Iadd.atleast a portion of said second tubular passing through one of said firsttubular or another tubular having an interior diameter greater than saidexterior diameter of said second tubular, .Iaddend.said methodcomprising .[.the following steps.].:inserting a downhole tool into saidwellbore; moving said downhole tool through said second tubular and pastsaid lower end of said second tubular; securing said downhole toolwithin said first tubular adjacent said window depth .Iadd.by activatingan anchor portion of said downhole tool to a diameter greater than theinternal diameter of said second tubular to secure said downhole tool tosaid first tubular.Iaddend.; inserting a cutting member into said firsttubular; guiding said cutting member with said downhole tool to cut saidwindow in said first tubular with said cutting member; retrieving saidcutting member from said wellbore; and retrieving said downhole toolfrom said wellbore .Iadd.through said second tubular.Iaddend..
 2. Themethod of claim 1, wherein .[.said step of.]. inserting a downhole toolinto said wellbore further comprises:inserting an anchor assembly intosaid wellbore; and subsequently inserting a whipstock assembly into saidwellbore.
 3. The method of claim 2, further comprising:connecting saidanchor assembly and said whipstock assembly together at a depth in saidwellbore greater than said lower end of said second tubular.
 4. Themethod of claim 2, wherein .[.said step of.]. retrieving said downholetool further comprises:simultaneously retrieving said anchor assemblyand said whipstock assembly.
 5. The method of claim 4, wherein .[.saidstep of.]. simultaneously retrieving further comprises:sequentiallyshearing first and second shearable members within said whipstockassembly and said anchor assembly, respectively.
 6. The method of claim5, .[.further comprising.]. .Iadd.wherein inserting said anchor assemblyfurther comprises.Iaddend.:shearing a third shearable member to separatesaid anchor assembly from a first wellbore transport member.
 7. Themethod of claim 6, .[.further comprising.]. .Iadd.wherein subsequentlyinserting a whipstock assembly further comprises.Iaddend.:shearing afourth shearable member to separate said whipstock assembly from asecond wellbore transport member.
 8. The method of claim 2, furthercomprising:.[.expanding.]. .Iadd.engaging .Iaddend.a lower portion of awhipstock assembly .[.into engagement.]. with said first tubular member.9. The method of claim 8, wherein .[.said step of.]. retrieving saiddownhole tool from said wellbore further comprises:.[.radiallyretracting.]. .Iadd.disengaging .Iaddend.said lower portion of saidwhipstock assembly .Iadd.from said first tubular member before saidwhipstock assembly is retrieved into said lower end of said secondtubular.Iaddend..
 10. The method of claim 1, wherein .[.the step of.].securing said downhole tool includes rotatably securing said downholetool .[.within.]. .Iadd.with respect to .Iaddend.said first tubular. 11.A method for removably positioning a whipstock in a first tubulardisposed within a borehole to cut a window in said first tubular,.Iadd.at least a portion of .Iaddend.the first tubular .[.containing.]..Iadd.positioned axially below .Iaddend.a second tubular .[.therein.].having .[.a.]. .Iadd.an interior .Iaddend.diameter .Iadd.and an exteriordiameter .Iaddend.less than .Iadd.an interior diameter of .Iaddend.saidfirst tubular, .Iadd.at least a portion of said second tubular passingthrough one of said first tubular or another tubular having an interiordiameter greater than said exterior diameter of said second tubular,.Iaddend.the method comprising .[.the steps of.].:positioning a supportmember within said first tubular; .[.expanding slips on said supportmember to secure.]. .Iadd.securing slips on .Iaddend.said support member.[.within.]. .Iadd.to .Iaddend.said first tubular .Iadd.axially belowsaid second tubular.Iaddend.; positioning said whipstock within saidfirst tubular; securing said whipstock to said support member;.[.radially expanding.]. .Iadd.engaging .Iaddend.a lower portion of saidwhipstock .[.to thereby engage a wall.]. .Iadd.with an inner diametersurface .Iaddend.of said first tubular; cutting said window in saidfirst tubular; .[.retracting said radially expanded.]. .Iadd.disengagingsaid .Iaddend.lower portion of said whipstock for retrieval of saidwhipstock through said second tubular .[.member.].; and .[.retractingsaid slips on said support member to release.]. .Iadd.releasing slips on.Iaddend.said support member .[.for retrieval of.]. .Iadd.from saidfirst tubular and retrieving said whipstock and .Iaddend.said supportmember through said second tubular.
 12. The method of claim 11, wherein.[.said step of retracting said radially expandable.]. .Iadd.disengagingsaid lower .Iaddend.portion of said whipstock further comprises:shearingat least one pin member.
 13. The method of claim 11, furthercomprising:simultaneously retrieving said support member and saidwhipstock through said second tubular.
 14. The method of claim 11,wherein .[.said step of.]. securing said whipstock to said supportmember further comprises:azimuthally orienting said whipstock withrespect to said support member.
 15. The method of claim 11, wherein.[.said step of radially expanding.]. .Iadd.securing .Iaddend.slips on asupport member further comprises:.[.expanding.]. .Iadd.moving.Iaddend.upper slips radially outwardly; and independently.[.expanding.]. .Iadd.moving .Iaddend.lower slips radially outwardly.16. The method of claim 11, wherein .[.said step of retracting saidslips on said support member to release.]. .Iadd.releasing slips on.Iaddend.said support member comprises:.[.retracting.]. .Iadd.moving.Iaddend.upper slips radially inwardly; and independently.[.retracting.]. .Iadd.moving .Iaddend.said lower slips radiallyinwardly.
 17. The method of claim 11, wherein .[.said step of expandingslips on a support member to secure.]. .Iadd.securing slips on.Iaddend.said support member .[.within.]. .Iadd.with .Iaddend.said firsttubular further comprises:supporting radial forces acting on .[.eachof.]. said slips with a first plurality of relatively slidable elements.18. The method of claim 17, further comprising:supporting torque forcesacting on said slips with keyed members disposed on each of said firstplurality of relatively slidable elements.
 19. A method for retrievablypositioning a downhole anchor within a first tubular supported within awellbore, .Iadd.at least a portion of .Iaddend.said first tubular.[.having therein.]. .Iadd.positioned axially below .Iaddend.a secondtubular .[.supported within said first tubular and.]. having .[.a.]..Iadd.an interior .Iaddend.diameter .Iadd.and an exterior diameter.Iaddend.less than .Iadd.an interior diameter of .Iaddend.the firsttubular, .[.said second tubular having a lower end within said firsttubular,.]..Iadd.at least a portion of said second tubular passingthrough one of said first tubular or another tubular having an interiordiameter greater than said exterior diameter of said second tubular, themethod .Iaddend.comprising .[.the following steps.].:connecting saiddownhole anchor to a wellbore transport member; inserting said downholeanchor and said wellbore transport member inside of said wellborecontaining said first tubular; moving said downhole anchor and saidwellbore transport member past .[.said.]. .Iadd.a .Iaddend.lower end ofsaid second tubular and into said first tubular; .[.expanding setting.]..Iadd.engaging .Iaddend.slips on said downhole anchor .[.to engage.]..Iadd.with .Iaddend.an inner .[.wall.]. .Iadd.diameter surface.Iaddend.of said first tubular; disconnecting said downhole anchor fromsaid wellbore transport member; retrieving said wellbore transportmember from said wellbore .Iadd.through said second tubular.Iaddend.;.[.retracting said setting.]. .Iadd.releasing .Iaddend.slips on saiddownhole anchor from said inner .[.wall.]. .Iadd.diameter surface.Iaddend.of said first tubular; and retrieving said downhole anchor fromsaid wellbore .Iadd.through said second tubular.Iaddend..
 20. The methodof claim 19, further comprising:supporting a whipstock assembly on saiddownhole anchor; and .[.expanding.]. .Iadd.engaging .Iaddend.a lowerportion of said whipstock assembly .[.to engage.]. .Iadd.with.Iaddend.said inner .[.wall.]. .Iadd.diameter surface .Iaddend.of saidfirst tubular.
 21. The method of claim 20, furthercomprising:.[.retracting.]. .Iadd.disengaging .Iaddend.said lowerportion of said whipstock assembly .[.to disengage.]. .Iadd.with.Iaddend.said inner .[.wall.]. .Iadd.diameter surface .Iaddend.of saidfirst tubular .Iadd.before said whipstock assembly is retrieved intosaid lower end of said second tubular.Iaddend..
 22. The method of claim20, further comprising:securing said whipstock assembly to a secondwellbore transport member; lowering said whipstock assembly through saidsecond tubular; and disconnecting said whipstock assembly from saidsecond wellbore transport member by shearing a shearable member.
 23. Themethod of claim 19, wherein .[.said step of retracting said setting.]..Iadd.releasing .Iaddend.slips further comprises:retracting at least oneupper slip; and independently retracting at least one lower slip.
 24. Amethod for removably positioning a whipstock in a first tubular disposedwithin a borehole to cut a window in said first tubular, .Iadd.a portion.Iaddend.of the first tubular .[.containing.]. .Iadd.positioned axiallybelow .Iaddend.a second tubular .[.therein.]. having .[.a.]. .Iadd.aninterior .Iaddend.diameter .Iadd.and an exterior diameter .Iaddend.lessthan .Iadd.an interior diameter of .Iaddend.said first tubular, .Iadd.atleast a portion of said second tubular passing through one of said firsttubular or another tubular having an interior diameter greater than saidexterior diameter of said second tubular, .Iaddend.the method comprising.[.the steps of.].:positioning a support member within said firsttubular; .[.expanding.]. .Iadd.securing .Iaddend.slips on said supportmember .[.to secure said support member within.]. .Iadd.with.Iaddend.said first tubular .Iadd.axially below said secondtubular.Iaddend.; positioning said whipstock within said first tubular;securing said whipstock to said support member; .[.radially expanding.]..Iadd.engaging .Iaddend.a lower portion of said whipstock .[.to therebyengage a wall.]. .Iadd.with an inner diameter surface .Iaddend.of saidfirst tubular; inserting a cutting member through the second tubular andinto said first tubular; .[.and.]. engaging said cutting member withsaid whipstock to cut said window in said first tubular.[...]..Iadd.;and retrieving said whipstock assembly from said wellbore through saidsecond tubular. .Iaddend.
 25. The method of claim 24, furthercomprising:.[.retracting said radially expanded.]. .Iadd.disengagingsaid .Iaddend.lower portion of said whipstock .Iadd.from said firsttubular .Iaddend.for retrieval of said whipstock through said secondtubular.
 26. The method of claim 25, .[.wherein said step of retractingsaid.]. .Iadd.further comprising.Iaddend.:.Iadd.releasing .Iaddend.slipson said support member .[.to release said support member comprises:.]..Iadd.from said first tubular by .Iaddend..[.retracting.]. .Iadd.moving.Iaddend.upper slips radially inwardly.[.;.]. and independently.[.retracting.]. .Iadd.moving .Iaddend.said lower slips radiallyinwardly.
 27. The method of claim 25, further comprising:simultaneouslyretrieving said support member and said whipstock through said secondtubular.
 28. The method of claim 24, wherein .[.said step ofexpanding.]. .Iadd.securing .Iaddend.slips on a support member furthercomprises:.[.expanding.]. .Iadd.moving .Iaddend.upper slips radiallyoutwardly; and independently .[.expanding.]. .Iadd.moving .Iaddend.lowerslips radially outwardly.
 29. The method of claim 24, wherein .[.saidstep of expanding.]. .Iadd.securing .Iaddend.slips on a support member.[.to secure said support member within.]. .Iadd.with .Iaddend.saidfirst tubular further comprises:supporting radial forces acting on eachof said slips with a first plurality of relatively slidable elements.30. A method for retrievably positioning a downhole anchor within afirst tubular supported within a wellbore, .Iadd.at least a portion of.Iaddend.said first tubular .[.having therein.]. .Iadd.positionedaxially below .Iaddend.a second tubular .[.supported within said firsttubular and.]. having .[.a.]. .Iadd.an interior .Iaddend.diameter.Iadd.and an exterior diameter .Iaddend.less than .Iadd.an interiordiameter of .Iaddend.the first tubular, .[.said second tubular having alower end within said first tubular,.]. .Iadd.at least a portion of saidsecond tubular passing through one of said first tubular or anothertubular having an interior diameter greater than said exterior diameterof said second tubular, the method .Iaddend.comprising .[.the followingsteps.].:inserting said downhole anchor inside of said wellborecontaining said first tubular; moving said downhole anchor past.[.said.]. .Iadd.a .Iaddend.lower end of said second tubular and intosaid first tubular; .[.expanding setting.]. .Iadd.engaging.Iaddend.slips on said downhole anchor .[.to engage.]. .Iadd.with.Iaddend.an inner .[.wall.]. .Iadd.diameter surface .Iaddend.of saidfirst tubular; .[.retracting said setting.]. .Iadd.releasing.Iaddend.slips on said downhole anchor from said inner .[.wall.]..Iadd.diameter surface .Iaddend.of said first tubular; and retrievingsaid downhole anchor from said wellbore .Iadd.through said secondtubular.Iaddend..
 31. The method of claim 30, wherein .[.the step of.].inserting said downhole anchor further comprises:interconnecting saiddownhole anchor and a well transport member; and thereafter insertingsaid downhole member and said well transport member inside of saidwellbore.
 32. The method of claim 30, further comprising:supporting awhipstock assembly on said downhole anchor; and .[.expanding.]..Iadd.engaging .Iaddend.a lower portion of said whipstock assembly .[.toengage.]. .Iadd.with .Iaddend.said inner .[.wall.]. .Iadd.diametersurface .Iaddend.of said first tubular.
 33. The method of claim 32,further comprising:.[.retracting.]. .Iadd.disengaging .Iaddend.saidlower portion of said whipstock assembly .[.to disengage.]. .Iadd.with.Iaddend.said inner .[.wall.]. .Iadd.diameter surface .Iaddend.of saidfirst .Iadd.tubular prior to retrieval of said whipstock assembly intosaid lower end of said second tubular.Iaddend..
 34. The method of claim30, wherein .[.said step of retracting said setting.]. .Iadd.releasing.Iaddend.slips further comprises:retracting at least one upper slip; andindependently retracting at least one lower slip. .Iadd.35. The methodof claim 1, wherein said downhole tool includes a whipstock and anchorslips, and retrieving said downhole tool comprises simultaneouslyretrieving said whipstock and said anchor slips from said wellborethrough said second tubular. .Iaddend..Iadd.36. The method as defined inclaim 35, wherein retrieving said downhole tool comprises: releasingsaid anchor slips from secured engagement with said first tubular beforesaid downhole tool is retrieved into said lower end of said secondtubular. .Iaddend..Iadd.37. The method of claim 35, wherein retrievingsaid downhole tool further comprises: shearing a shearable member toeffect releasing of said anchor slips from secured engagement with saidfirst tubular. .Iaddend..Iadd.38. The method of claim 35, whereinretrieving said downhole tool further comprises:releasing a rachet lockassembly to permit said anchor slips to move radially inward fromsecured engagement with said first tubular. .Iaddend..Iadd.39. Themethod of claim 1, further comprising: said downhole tool includes awhipstock and anchor slips; and azimuthally orientating said whipstockwith respect to said anchor slips while connecting said whipstock tosaid anchor slips secured to said first tubular. .Iaddend..Iadd.40. Themethod of claim 19, wherein said downhole anchor includes a whipstock,and retrieving said downhole anchor comprises simultaneously retrievingsaid whipstock and said slips from said wellbore through said secondtubular. .Iaddend..Iadd.41. The method of claim 40, wherein retrievingsaid downhole anchor comprises:releasing said slips from securedengagement with said first tubular before said downhole anchor isretrieved into said lower end of said second tubular. .Iaddend..Iadd.42.The method of claim 40, wherein retrieving said downhole anchor furthercomprises: shearing a shearable member to effect releasing of said slipsfrom secured engagement with said first tubular. .Iaddend..Iadd.43. Themethod of claim 40, wherein retrieving said downhole anchor furthercomprises: releasing a rachet assembly to permit said slips to moveradially inward from secured engagement with said first tubular..Iaddend..Iadd.44. The method of claim 19, furthercomprising:azimuthally orientating whipstock with respect to said slipswhile connecting said whipstock to said slips secured to said firsttubular. .Iaddend..Iadd.45. The method of claim 30, wherein saiddownhole anchor includes a whipstock, and retrieving said downholeanchor comprises simultaneously retrieving said whipstock and said slipsfrom said wellbore through said second tubular. .Iaddend..Iadd.46. Themethod of claim 45, wherein retrieving said downhole anchor comprises:releasing said slips from secured engagement with said first tubularbefore said downhole anchor is retrieved into said lower end of saidsecond tubular. .Iaddend..Iadd.47. The method of claim 45, whereinretrieving said downhole anchor further comprises:shearing a shearablemember to effect releasing of said slips from secured engagement withsaid first tubular. .Iaddend..Iadd.48. The method of claim 45, whereinretrieving said downhole anchor further comprises:releasing a rachetassembly to permit said slips to move radially inward from securedengagement with said first tubular. .Iaddend..Iadd.49. The method ofclaim 30, further comprising:azimuthally orientating a whipstock withrespect to said slips while connecting said whipstock to said slipssecured to said first tubular. .Iaddend.